Some conventional indoor air quality (“IAQ”) monitors typically include a housing, a filter cassette or cartridge within the housing, a pump operable to draw an airflow through the filter cartridge, and a single impactor positioned adjacent an inlet to an air passageway in the housing upstream of the filter cartridge. Impactors are typically configured to trap or filter particulates having a particular nominal size or greater (e.g., 10 microns or greater) to substantially prevent such particles from entering the air passageway and being collected in the filter cartridge. The single impactor is typically removable from the housing and can be replaced with another single impactor of a different size to trap or filter different-size particulates. Other conventional IAQ monitors include a real-time measuring system (e.g., an optical engine), rather than the filter cartridge, to immediately display the results of an indoor air quality test.